This application relates to laser eye surgery of the crystalline lens using photodisruption caused by laser pulses.
Surgical procedures for removal of the crystalline lens utilize various techniques to break up the lens into small fragments that can be removed from the eye through incisions. Some of these procedures use manual instruments, ultrasound, heated fluids or lasers. One of the significant drawbacks of these methods is the need to actually enter the eye with probes in order to accomplish the fragmentation. This typically requires making large incisions on the lens and limits the precision associated with such lens fragmentation techniques.
Photodisruptive laser technology can deliver laser pulses into the lens to optically fragment the lens without insertion of a probe and thus is potentially a less intrusive procedure, offering higher precision and control.
Laser-induced photodisruption has been already used in the past in laser ophthalmic surgery. In the target region the laser ionizes a portion of the molecules, eventually releasing gases, which, in an expansion phase, disrupt and break up the lens material in the target region. In some cases Nd:YAG lasers have been employed as the laser sources.
Lens fragmentation via laser-induced photodisruption has also been proposed. For example, L'Esperance in U.S. Pat. No. 4,538,608 disclosed an apparatus for lens tissue destruction which included a viewing system, a laser and a means for optical delivery and scanning of the focal spot of laser pulses. The laser pulses were focused on the anterior plane of the lens and were moved progressively deeper into the lens to achieve cataract material destruction. In U.S. Pat. No. 5,246,435, Bille proposed an alternative approach that focused the laser pulses first in a posterior region of the lens and then move the focus in a posterior to anterior direction. In this method the laser reached the target regions with less distortion from the already treated regions, thus affording greater control. However, various technical problems remain unresolved.